Low-loss magnetic powder core, and switching power supply, active filter, filter, and amplifying device using the same

Abstract

A magnetic powder core comprises a molded article of a mixture of a glassy alloy powder and an insulating material. The glassy alloy comprises Fe and at least one element selected from Al, P, C, Si, and B, and has a texture primarily composed of an amorphous phase. The glassy alloy exhibits a temperature difference ΔT x , which is represented by the equation ΔT x =T x −T g , of at least 20 K in a supercooled liquid, wherein T x indicates the crystallization temperature and T g indicates the glass transition temperature. The magnetic core precursor is produced mixing the glassy alloy powder with the insulating material, compacting the mixture to form a magnetic core precursor, and annealing the magnetic core precursor at a temperature in the range between (T g −170) K and T g K to relieve the internal stress of the magnetic core precursor. The glassy alloy exhibits low coercive force and low core loss.

1. An active filter comprising:
 a boosting converter circuit comprising: 
 a switching element;  
 a coil provided with a magnetic core generating a back electromotive force when the switching element breaks a DC current, wherein the magnetic core comprises molded article of a mixture of a glassy alloy powder and an insulating material, the glassy alloy powder having a texture primarily composed of an amorphous phase and exhibiting a temperature difference ΔT x , which is represented by the equation ΔT x =T x −T g , of at least 20° K. in a supercooled liquid, wherein T x  indicates the crystallization temperature and T g  indicates the glass transition temperature;  
 a rectifying element connected in series in the forward direction to the coil provided with the magnetic core for rectifying a current generated by the back electromotive force; and  
 a capacitor for smoothing the rectified current; and  
 a control unit for controlling the switching interval of the switching element of the boosting converter circuit.